Place the rice in a colander and rinse in cold water; drain. In a medium saucepan, bring the water to a boil and season lightly with salt. Stir in the rice and bring to a boil over high heat. Reduce the heat to low, cover and simmer for 15 minutes. Remove the saucepan from the heat and let stand, covered, for 5 minutes, then fluff the rice with a fork.
Meanwhile, melt the butter in a large skillet. Add the onion and cook over moderately high heat, stirring frequently, until golden brown, about 7 minutes. Add the garlic and cook for 30 seconds. Add the shrimp and a pinch of cayenne and cook, stirring, until the shrimp are opaque, about 3 minutes; season with salt. Remove the skillet from the heat and stir in the rice. Transfer the shrimp and rice to a platter, sprinkle with the parsley and serve.
A refreshing New World Chenin Blanc will have the soft acidity to contrast with the edge of spice in this dish and to blend with the sweetness of the shrimp.